Phase relations in the ternary systems PrFeM (M  Ga, In, Tl)

Abstract

In search for novel hard magnetic materials, the phase relations in the (praseodymium, iron)-rich region of the ternary systems PrFeM (M  Ga, In,Tl) have been determined in partial isothermal sections at 780°C, employing room temperature X-ray diffraction analysis of alloys which were arc melted, annealed at 780°C for 72 h and quenched. Phase equilibria in all cases are determined by a stable two-phase equilibrium between the α-Fe solid solution and PrM (M  Ga,In,Tl). Comparing aluminium, gallium, indium and thallium alloys there is a considerable decrease of the solid solubility of the metal in binary Pr 2Fe 17 with increasing ordinal number of the metal. A similar decrease is observed from the solid solubility of iron in the compounds of the binary systems Pr-M. In each of the ternary systems investigated, a ternary compound is observed at 780°C. Pr 6Fe 13In and Pr 6Fe 13Tl crystallize with an ordered structure variant of the La 6Co 11Ga 3 type, whereas Pr 6Fe 11Ga 3 is isotypic with the partially ordered La 6Co 11Ga 3 type and is formed from a ternary peritectoid reaction at around 800°C Pr 2Fe 17− x Ga x + Pr 5Ga 3 + l ⇌ Pr 6Fe 11Ga 3 In the praseodymium-rich region of each of the phase diagrams, liquid is observed, which at 780°C forms a two-phase equilibrium with each of the ternary compounds.